1. Technical Field
The present invention relates to wireless power transmission technology and, more particularly, to a rectifier in a wireless power reception apparatus.
2. Description of the Related Art
Wireless power transmission technology based on electromagnetic waves initially started with technology for sending power over a long or short distance in such a manner that a power transmitter sends electromagnetic waves having high energy in a desired direction and a power receiver receives the transmitted electromagnetic waves, and has not overcome the problem in which it has very low efficiency and is harmful to the human body.
Wireless power transmission technology using magnetic induction scheme has been attempted since the discovery of a magnetic induction phenomenon, and includes many commercialized cases. However, distance allowable between power transmitter and power receiver is very short, a large amount of heat is generated, usability is bad because charging efficiency highly varies depending on the locations of the power transmitter and the power receiver, and, above all, the amount of transmission power is limited.
Wireless power transmission technologies that had been at standstill as described above are dramatically advancing after Martin Soljacic at MIT announced a new transmission technology using magnetic resonance scheme in 2007.
Magnetic resonance is evanescent wave coupling phenomenon in which when two media resonate at the same frequency, electromagnetic waves move from one medium to the other medium through short-distance magnetic field. The wireless power transmission technology using a magnetic resonance scheme can transfer higher power to farther location with very high efficiency.
The rectifier of a wireless power reception apparatus performs function similar to that of a common Alternating Current (AC)-Direct Current (DC) rectifier. The efficiency of the rectifier exerts large influence on the overall efficiency of wireless power transmission. Passive rectifiers using diode bridges suffer from loss in peak voltage due to voltage drop generated by diodes.
This voltage drop problem can be overcome using active elements, instead of the diodes. Reverse current leakage may be generated inversely from DC output to AC input in the diode-connected active elements depending on sections of AC input waveform. Such leaking reverse current degrades efficiency.
Although such reverse current can be reduced by fully turning off the diode-connected active elements depending on sections of AC input waveform, reverse current may still occur during a delay time because it takes time to turn off the active elements.